Lindsay Meyer
(Dianna Zosche)
Three-dimensional Ultrasound:
Techniques and Applications in Obstetrics
Page 1 of 11
Abstrac...
Lindsay Meyer
(Dianna Zosche)
Introduction
“Ultrasound” is the vernacular term for medical sonography, a non-invasive imag...
Lindsay Meyer
(Dianna Zosche)
From 2D to 3D – Imaging Techniques
Conventional, 2D ultrasound relies on the reflection of h...
Lindsay Meyer
(Dianna Zosche)
The third and final step to 3D ultrasound is visualization. For optimal image perception,
de...
Lindsay Meyer
(Dianna Zosche)
Common Congenital Anomalies
Embryology texts suggest the incidence of birth defects to be ap...
Lindsay Meyer
(Dianna Zosche)
considered life-threatening and occurs in 1-2 live births per 1000, with a higher incidence ...
Lindsay Meyer
(Dianna Zosche)
3D ultrasound. The study made a definitive diagnosis of 79% of defects with 2D ultrasound (n...
Lindsay Meyer
(Dianna Zosche)
Comparitive Diagnosis of Prenatal Malformations
69%
0%
50%
97%
88%
100%
100%
97%
0% 20% 40% ...
Lindsay Meyer
(Dianna Zosche)
In addition to improved detection of prenatal malformations, 3D ultrasound has provided
an u...
Lindsay Meyer
(Dianna Zosche)
applications helps perpetuate awareness of its inherent diagnostic value. Assessing the valu...
Lindsay Meyer
(Dianna Zosche)
References
Dyson, R., Pretorius, D., Budorick, N., Johnson, D., Sklansky, M., Cantrell, C., ...
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Three-dimensional Ultrasound: Techniques and Applications in Obstetrics

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Ultrasound has been used in medicine for over half a century, and is recognized as a non-invasive, non-radiative, and inexpensive imaging modality. Three-dimensional (“3D”) medical imaging is now being widely employed in the clinical setting. This report reviews the development of ultrasound, its method of function, and its practical applications of 3D ultrasound in fetal embryology and obstetrics.

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Transcript of "Three-dimensional Ultrasound: Techniques and Applications in Obstetrics"

  1. 1. Lindsay Meyer (Dianna Zosche) Three-dimensional Ultrasound: Techniques and Applications in Obstetrics Page 1 of 11 Abstract Ultrasound has been used in medicine for over half a century, and is recognized as a non- invasive, non-radiative, and inexpensive imaging modality. Three-dimensional (“3D”) medical imaging is now being widely employed in the clinical setting. This report reviews the development of ultrasound, its method of function, and its practical applications of 3D ultrasound in fetal embryology and obstetrics.
  2. 2. Lindsay Meyer (Dianna Zosche) Introduction “Ultrasound” is the vernacular term for medical sonography, a non-invasive imaging technique used in diagnosing disease and developmental defects. In physics, “ultrasound” refers to acoustic energy outside the range of human hearing. Medical sonographic scanners typically operate between two and 18 megahertz, with a unique relationship between resolution and depth. Lower frequencies penetrate body tissues deeper than higher frequencies, but produce lower image resolution (and vice-versa). The improving economics of 3D ultrasound technology coupled with advances in 3D image visualization have made the technique increasingly routine for pregnant women in the past decade. This paper is meant to achieve two goals. First, an exploration of the origin of ultrasound will provide the basis for building a compelling case for the use of 3D ultrasound. Second, a discussion of common congenital anomalies will illustrate the efficacy of the technology. A Brief History of Ultrasound In 1950, the first commercial “ultrasonic locator” became available by General Precision Laboratories (Woo, 2002). George Ludwig, a Naval Officer in Bethesda, Maryland first began experimenting with the conduction of pulse-echo techniques several years prior. His methodology was similar to the radar utilized by the military to detect the presence of foreign boats or flying objects. Ludwig collaborated with physicists and engineers to study gallstones in muscle tissues in the human body. Using a transducer to send and receive high-frequency sound waves at a rate of 60 pulses per second, Ludwig recorded reflections with an oscilloscope to detect the presence and position of foreign bodies. Much of this early work with ultrasound was clandestine until 1949 because the information was considered classified naval information. Page 2 of 11
  3. 3. Lindsay Meyer (Dianna Zosche) From 2D to 3D – Imaging Techniques Conventional, 2D ultrasound relies on the reflection of high frequency sound waves by bones and muscles. Soft tissue and hollow structures do not reflect the waves and appear dark. Anywhere there are changes in density in the body, sound waves are generally reflected. This technology was prevalent around the world for nearly half a century. In 1994, 3D ultrasound was popularized in the European Journal of Ultrasound and detailed three discrete steps – scanning, reconstruction, and visualization. Four scanning techniques (mechanical, free-hand with position sensing, free-hand without position sensing, 2D array) exist. Among these methods, mechanical scanning is most relevant to medicine because the relative position and orientation of each image can be known precisely. This approach uses a scanning apparatus (transducer) to acquire 2D ultrasound images over the area of interest (Fenster, Downey & Cardinal, 2000). In the reconstruction step, 2D images are placed in their correct relative positions and orientations in the 3D image volume (Fenster et al., 2002). Feature-based reconstruction uses anatomical structures to determine boundary surfaces, offering efficient manipulation by computer. In contrast, the more popular voxel method of reconstruction uses a Cartesian grid to build elements in three dimensions. Each 2D coordinate (x, y) is interpolated to determine a 3D coordinate (x, y, z). Automated reference tables stored in computers help accelerate this process. The voxel approach preserves all original information and enables the generation of new views not in the original set of 2D images. This method is also superior because it allows the operator to use different segmentation and classification schemes to segment boundaries, measure volume or perform various volume-based rendering (Fenster et al., 2000). Page 3 of 11
  4. 4. Lindsay Meyer (Dianna Zosche) The third and final step to 3D ultrasound is visualization. For optimal image perception, depth shading and color and texture mapping is used. Volume rendering helps to approximate the passage of light through soft tissues. Computer algorithms have vastly simplified this process of manipulating and isolating images. Dynamic 3D imaging is used to show fluid motion within the fetus and is a consequence of continued technological improvements. 12/9/2007 4:21 PMMedical Physics Presentation © 9 Scan  Uses traditional 2D apparatus (transducer)  Acquires a series of 2D images  Real-time, fast acquisition  Computer integrates 2D images into 3D volume  Computer matches 2D and 3D coordinates Reconstruct  Images are colored and shaded  Manipulation of image; isolation of structures  Dynamic 3D imaging (4D) Visualize Building a Case for 3D Ultrasound In conventional, two-dimensional (2D) ultrasounds, physicians were left to mentally integrate multiple 2D images to understand 3D structures. This guesswork introduced a high margin of error in addition to prohibiting the imaging of certain anatomical features. As 2D ultrasounds capture images at randomized planes, generating the same picture more than once is nearly impossible (Fenster et al., 2000). This impedes effective therapeutic monitoring. It also increases the risk of incorrect diagnosis. Systematically assessing fetal development is compromised in 2D ultrasound because accurate volume estimations are difficult to make. Each of these obstacles was overcome with the development of 3D ultrasound. Page 4 of 11
  5. 5. Lindsay Meyer (Dianna Zosche) Common Congenital Anomalies Embryology texts suggest the incidence of birth defects to be approximately 5%. For the purposes of this paper, common congenital anomalies have been classified into four groups – those of the body surface, extremities, spine, and cranium/face. The development of 3D ultrasound has improved the detection of several anomalies in each of these four groups (Xu et al, 2002). Conjoined twins, tumors, edema, and placental defects are abnormalities of the body surface. Difficult to detect and diagnose, these conditions vary in severity. Teratomas result from the unregulated division of pluripotent (stem) cells. Sacrococcogeal teratomas appear at the base of the tailbone and are the most common type of tumor in newborns. These teratomas can obstruct the normal passage of fluids from surrounding organs. Placental defects include placental previa (placenta impedes the cervix) and placental abruption (placental lining separates from the uterus). Often fatal to infant and mother, these conditions are associated with heavy bleeding late in pregnancy and require careful monitoring. Poldactyly, a condition in which too few or too many fingers or toes develop is a common defect of the extremities caused by genetic mutation. It may also occur as part of a cluster of defects related to teratogen-induced syndromes (i.e.: fetal alcohol syndrome, Accutane- exposure). Other defects to the extremities include stunted growth (osteogenesis imperfecta) and club foot. This class of defects is not Page 5 of 11 12/9/20076:54PMMedicalPhysicsPresentation© 6 RepresentativeMedicalCases Commoncongenitalanomalies BodySurface Conjoinedtwins Tumors Edema Placentaldefects Extremities Polydactyly Limbdefects Osteogenesis imperfecta Clubfoot Spine Spinabifida Scoliosis Neuraltube defects Cranium/Face Cleftlip Cleftpalate Hydrocephalus Anencephaly 12/9/20076:55PMMedicalPhysicsPresentation© 6 RepresentativeMedicalCases Commoncongenitalanomalies BodySurface Conjoinedtwins Tumors Edema Placentaldefects Extremities Polydactyly Limbdefects Osteogenesis imperfecta Clubfoot Spine Spinabifida Scoliosis Neuraltube defects Cranium/Face Cleftlip Cleftpalate Hydrocephalus Anencephaly
  6. 6. Lindsay Meyer (Dianna Zosche) considered life-threatening and occurs in 1-2 live births per 1000, with a higher incidence in males. Spina bifida is a condition in which the neural tube does not close. While surgery can correct the opening, affected individuals will experience reduced quality of life due to nerve and spinal cord dysfunction. Some fetuses with the condition will spontaneously abort. Research by Kurjak, Pooh, Merce, Carrera, Salihagic-Kadic & Andonotopo (2005) suggested that the condition could be diagnosed with 3D ultrasound at 9 weeks gestation. In addition to neural tube defects, scoliosis can also be diagnosed with 3D ultrasound. Environmental influences such as maternal retinoid intake and cigarette smoking may interact with genetics to cause cleft lip and cleft palate. Hydrocephalus is caused by an accumulation of cerebrospinal fluid and manifests in an abnormally large head. The defect occurs in approximately one of every 500 live births and is more common than Down syndrome. Anencephaly is a disorder in which infants are born without a forebrain. If spontaneous abortion or stillbirth does not occur, death occurs shortly after delivery. Applications Study data released by Xu, Zhang, Lu & Ziao in 2002 compared the efficacy of 2D and 3D ultrasounds on the basis of accurate diagnosis of prenatal malformations. For the four categories of congenital anomalies outlined above, the study showed diagnostic superiority with Page 6 of 11 12/9/20076:54PMMedicalPhysicsPresentation© 6 RepresentativeMedicalCases Commoncongenitalanomalies BodySurface Conjoinedtwins Tumors Edema Placentaldefects Extremities Polydactyly Limbdefects Osteogenesis imperfecta Clubfoot Spine Spinabifida Scoliosis Neuraltube defects Cranium/Face Cleftlip Cleftpalate Hydrocephalus Anencephaly 12/9/20077:11PMMedicalPhysicsPresentation© 6 RepresentativeMedicalCases Commoncongenitalanomalies BodySurface Conjoinedtwins Tumors Edema Placentaldefects Extremities Polydactyly Limbdefects Osteogenesis imperfecta Clubfoot Spine Spinabifida Scoliosis Neuraltube defects Cranium/Face Cleftlip Cleftpalate Hydrocephalus Anencephaly
  7. 7. Lindsay Meyer (Dianna Zosche) 3D ultrasound. The study made a definitive diagnosis of 79% of defects with 2D ultrasound (n = 49). The use of 3D ultrasound improved the percentage of correct diagnoses to 94% (n = 58). In 60% of cases (n = 35), malformations were correctly diagnosed by both 2D and 3D ultrasound but the use of 3D ultrasound provided better qualitative diagnostic information. Extrapolating this 15% improvement in correct diagnoses to larger populations suggests a cascade of public health benefits associated with early detection of defects and improved prenatal care. Aggregating data from the Xu et al. (2002) study demonstrated that detection of craniofacial anomalies was 19% greater with 3D ultrasound (n = 30). No apparent difference between ultrasound modalities for the body surface (n = 26) reflects the reality that diagnosing these defects in utero can be extremely challenging. This study also left out conjoined twins, a rare abnormality, but one that is easily detected with 3D ultrasound. All spinal defects were detected with 3D ultrasound, but the low sample size (n =4) may overstate the comparative diagnostic usefulness of 3D technology. Low sample size (n = 2) was also encountered with defects to the extremities, reducing the integrity of the suggested 50% improvement in diagnosis with 3D ultrasound. Page 7 of 11
  8. 8. Lindsay Meyer (Dianna Zosche) Comparitive Diagnosis of Prenatal Malformations 69% 0% 50% 97% 88% 100% 100% 97% 0% 20% 40% 60% 80% 100% Cranium/face Spine Extremities Body surface % of correct diagnoses (2D) % of correct diagnoses (3D) Kurjak et al. (2005) showed that structural and functional developments in the first 12 weeks of gestation could be assessed more objectively and reliably with 3D ultrasound. Because the first trimester presents the greatest risk of developmental abnormalities, accurate fetal monitoring during this period is critical. The anatomy and physiology of embryonic development is a field where medicine exerts its greatest impact on early pregnancy and is a foray into fascinating aspects of embryonic differentiation (Kurjak et al., 2005). Dyson, Pretorius, Budorick, Johnson, Skylansky, Cantrell, et al. (2000) suggested that 3D images were useful in counseling patients about the severity of fetal abnormalities. Dyson et al. also determined that the level of diagnostic confidence was heightened and used to support diagnoses made on the basis of 2D ultrasound images. Clinical Correlates Page 8 of 11
  9. 9. Lindsay Meyer (Dianna Zosche) In addition to improved detection of prenatal malformations, 3D ultrasound has provided an unintended benefit by strengthening the maternal-fetal bonding process. Ji, Pretorius, Newton, Uyans, Hull, Hollenbach et al. (2004) found that mothers who received 3D ultrasound showed their ultrasound images to more people than mothers receiving 2D ultrasounds alone. Seventy percent of mothers who had 3D ultrasounds felt that they “knew” their baby immediately after birth versus 56% of mothers that had 2D ultrasounds, reflecting the fact that 82% of mothers who had 3D ultrasounds had a tendency to form a mental picture of their child, post-examination. This contrasts with the 39% of subjects who began to picture their infant after having a 2D ultrasound. Image quality of 2D ultrasounds has improved but most laypersons are not equipped to understand even the highest resolution 2D images. Three-dimensional ultrasounds produce more recognizable images, improving the maternal-fetal bonding process. Conclusion As medicine continues to evolve, imaging techniques will concurrently improve to address the challenges of modern science. The advent of 3D ultrasound technology represents one giant leap for medical imaging. Three-dimensional ultrasound provides accurate representation of internal structures and improved visualization capacity. By integrating traditional 2D imaging techniques with 3D ultrasound, clinicians improve the statistical probability of accurate diagnoses. Detection of congenital anomalies affords parents and physicians substantial latitude in formulating and implementing prenatal care regiments, thereby improving public health. The prevalence of 3D ultrasound in obstetric exams is increasing as the technology becomes more cost-effective. As this trend continues, it offers the potential for safe, non- invasive monitoring of fetal development. Drawing attention to 3D ultrasound and its medical Page 9 of 11
  10. 10. Lindsay Meyer (Dianna Zosche) applications helps perpetuate awareness of its inherent diagnostic value. Assessing the value of 3D ultrasound encourages economic investment in improved medical technologies and propels continued innovation, raising standards of care. Page 10 of 11
  11. 11. Lindsay Meyer (Dianna Zosche) References Dyson, R., Pretorius, D., Budorick, N., Johnson, D., Sklansky, M., Cantrell, C., et al. (2000). Three-dimensional ultrasound in the evaluation of fetal anomalies. Ultrasound in Obstetrics and Gynecology, 16, 321-28. Fenster, A., Downey, D., Cardinal, H. (2001). Three-dimensional ultrasound imaging. Physics in Medicine and Biology, 46, R67-99. Ji, E., Pretorius, D., Newton, R., Uyan, K., Hull, A., Hollenbach, K. et al. (2005). Effects of ultrasound on maternal-fetal bonding: a comparison of two- and three-dimensional imaging. Ultrasound in Obstetrics and Gynecology, 25, 473-77. Kurjak, A., Pooh, R., Merce, L., Carrera, J., Salihagic-Kadic, A. & Andonotopo, W. (2005). Structural and functional early human development assessed by three-dimensional and four-dimensional sonography. Fertility and Sterility, 84(5), 1285-1299. Medical ultrasonography. (2007, December 7). In Wikipedia, The Free Encyclopedia. Retrieved December 9, 2007, from http://en.wikipedia.org/w/index.php? title=Medical_ultrasonography&oldid=176296551 Woo, Joseph (2002). A short history of the development of ultrasound in obstetrics and gynecology. http://www.ob-ultrasound.net/history1.html Xu, H., Zhang, Q., Lu, M., Xiao, X. (2002). Comparison of two-dimensional and three- dimensional sonography in evaluating fetal malformations. Journal of Clinical Ultrasound, 30, 515-25. Page 11 of 11

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